Display devices recently used in TVs, PCs, and mobile phones are commonly produced using a substrate such as a glass substrate as a base. On the substrate, a circuit element, a control element, and the like are mounted to form a display device.
Various skills are exercised in production of these display devices for achieving high resolution display. For example, in a display region, a plurality of gate wirings and a plurality of source wirings are respectively arranged in the row direction and in the column direction, and each pixel has a translucent pixel electrode and a switching element for controlling electrical conduction between the pixel electrode and each wiring so that each pixel is individually controlled.
For a specific example, in a liquid crystal display device having a pair of substrates sandwiching a liquid crystal layer, one of the substrates is a substrate having the above-mentioned wirings and the like so that the tilt of liquid crystal molecules in the liquid crystal layer may be controlled in each pixel, thereby realizing high-resolution liquid crystal display (see Patent Literature 1). Here, a substrate in which an active element such as a thin film transistor (TFT) is used as a switching element and pixel electrodes are arranged in a matrix is also referred to as an active matrix substrate.
Favorable materials forming the pixel electrodes include metal oxides such as ITO (Indium Tin Oxide) having translucency. Favorable materials forming the gate wiring, the source wiring, and electrodes in the TFT include metals having a low specific resistance such as aluminum (Al), and copper (Cu), and further include metals such as chromium (Cr), titanium (Ti), and molybdenum (Mo). The pixel electrodes and each wiring may be formed by stacking these materials on a substrate by sputtering and then patterning the materials into desired shapes by photolithography (see Patent Literature 2).